In recent years, thermoacoustic devices employing a thermoacoustic effect which is a conversion phenomenon between thermal energy and sound energy are proposed. For example, JP-A-2008-101910 (Patent Literature 1) discloses a thermoacoustic device in which a first stack and a second stack are disposed within a loop pipe. The first stack is sandwiched between a first high-temperature side heat exchanger and a first low-temperature side heat exchanger. The second stack is sandwiched between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger. In the thermoacoustic device, a self-excited sound wave is generated by a temperature gradient generated in the first stack. The second low-temperature side heat exchanger can be cooled by this sound wave.
JP-A-2008-101910 discloses a technique in which efficiency of heat exchange in the stack is improved by appropriately setting a length of the loop pipe, a state of a working fluid enclosed in the loop pipe, a diameter of a conduction path of the first stack and the second stack, and the like.
JP-A-2012-159266 (Patent Literature 2) discloses a configuration in which a blocking wall for blocking moving gas is installed in a pipe in which a motor and a refrigerator are formed. The blocking wall is installed so as to be capable of vibrating accompanying with vibration of gas. A circulation flow of the gas is prevented by the blocking wall. As a result, cooling insufficiency caused by the circulation flow of the gas is prevented.
JP-A-2011-127870 (Patent Literature 3) discloses a thermoacoustic engine, which includes: a first loop pipe in which a motor is disposed to convert thermal energy into sound energy; a second loop pipe in which a passive device is disposed to convert sound energy into thermal energy; and a connection pipe that connects the first loop pipe and the second loop pipe to each other. A vibrator that separates a working fluid of the first loop pipe and a working fluid of the second loop pipe is provided in the connection pipe. The vibrator is configured to be capable of vibrating in a vibration direction of a working fluid. The two separated working fluids and the vibrator vibrate at a predetermined resonance frequency. As a result, a sound wave is generated at a frequency lower than a frequency defined by loop lengths of the first loop pipe and the second loop pipe. Therefore, the same effect as in a case where a resonance pipe having a length equal to or longer than three times the loop lengths of the first loop pipe and the second loop pipe is provided between the first loop pipe and the second loop pipe is obtained. Since the resonance pipe having such a length is thus made unnecessary, the thermoacoustic engine can be downsized, and sound wave attenuation can be reduced.